Tree and stem tables are dataframes that store data from one specific census of one specific census plot. For any given plot one tree table stores data recorded during one specific census, and each row records the data from one specific tree. Similarly, for any given plot one stem table stores data recorded during one specific census , and each row records the data from one specific stem. For example, if plot X was censused twice, then it has two tree tables and two stem tables.
http://ctfs.si.edu/Public/CTFSRPackage/index.php/web/data_format
Each tree (or stem) table of a census plot has two remarkable properties:
The number of rows equals the number of trees (or stems) that were ever found in the plot (in any census). This implies that the number of rows is identical to that of any other tree (or stem) table of the same plot; also, that trees (or stems) appear in tree (or stem) tables before they recruit, while they are alive, and after they die.
The order of the rows is identical to that of any other tree (or stem) table of the same plot. This implies that you can compare data across censuses even if the row order is important for your analyses. Also, you can easily repeat analyses with different censuses with minimal effort. For example, this structure makes helps to calculate demographic rates between any pair of censuses.
treeID: The unique tree identifier in CTFS database. Useful to be certain
in matching trees.
stemID: The unique stem identifier in CTFS database. Useful to be certain
in matching stems.
tag: Tag number used in the field.
StemTag: Tag number on the individual stem, if present.
sp: The species mnemonic. To get full species names, the taxonomy table
must be downloaded from the CTFS database:
http://ctfs.arnarb.harvard.edu/CTFSReports
quadrat: Quadrat designation.
gx: The x coordinate within the plot, relative to one edge of the plot.
gy: The y plot coordinate.
MeasureID: The unique identifier of a single measurement in the CTFS
database.
CensusID: The numeric identifier of the census.
dbh: Diameter of one stem on the tree, the stem whose stemID is given.
pom: The point-of-measure, where the diameter was taken, identical to hom,
but a character variable with only 2 decimal places.
hom: The height-of-measure, identical to pom but a numeric variable with
full precision.
ExactDate: The date on which a tree was measured.
DFstatus: The codes for the measurement as recorded in the field.
A: Alive.
D: Dead.
lost_stem (deprecated): Lost stem. It usually means the stem was broken
in the given census, while the tree had no other stem. This status is
deprecated; it is safer to check stemID to determine whether a tree's
measurement changed stems between censuses.
M: Missing. It is used where there is no record of the corresponding
value of dbh, so it is not certain whether the tree was alive or dead.
P: Prior. It indicates a tree had not yet recruited at this census.
nostems: The number of living stems on the date of measurement.
status: Indicates the status of the entire tree. For example, if any stem
is alive, the tree is alive; if every stem is dead, the tree is dead:
A: Alive.
D: Dead.
M: Missing.
P: Prior. It indicates a tree had not yet recruited at this census.
G: Gone. xxx to complete.
date: The julian date, for date arithmetic.
agb: Above-ground-biomass of all stems on the tree, in Mg (equal to
metric tons or 106 g). Note that agb = 0 for dead trees.
Compared to tree tables, the the variables are and mean the same. But notice
some differences in DFstatus and agb; also notice the additional
variables codes and countPOM and that the variable nostems does not
exist for stem tables.
treeID: See tree table.
stemID: See tree table.
tag: See tree table.
StemTag: See tree table.
sp: See tree table.
quadrat: See tree table.
gx: See tree table.
gy: See tree table.
MeasureID: See tree table.
CensusID: See tree table.
dbh: Diameter of the stem.
pom: See tree table.
hom: See tree table.
ExactDate: See tree table.
DFstatus: The codes are the same as in tree tables except that stems may
have the additional status G (gone). G applies when a tree is alive and a
stem which formerly had a measurement does not in this census. This happens
in some plots, where individual stems do not have tags and cannot be tracked.
codes: The codes for the measurement as recorded in the field.
countPOM: The number of POMs (HOMs) for the same stem in this census.
status: See tree table.
date: See tree table.
agb: Same, but notice that some may be NA.
Other census tables.: bciYYsNmini,
bciYYtNmini